No power

[DH15]

I have a 2005 GMC Sierra with a 5.3.  It starts and idles fine but as soon as you try to put it under load it just dies.  It has new catalytic converters, new O2 sensors, and a second new fuel pump.  Fuel pressure at ignition on and idle is 60 psi but as soon as you accelerate it drops to 20 psi or less.  should note that this fuel system has the fuel pressure regulator with the pump.  Also, no codes set.  I am at a loss.  any suggestions would be appreciated. 

[Colossus]

any chance of fuel line collapse/crimped somewhere?  Filter clogged?(it is likely in the tank) bad fuel pressure regulator? 

[DH15]

Thanks for the input.  The pressure regulator and filter are part of the new fuel pump assembly.  I am leaning towards a problem with the fuel line.  That is what i intend to check and/or replace next.  Thanks again.

[Colossus]

You bet.  Keep us posted.  And as I and a few others have discovered the hard way, sometimes even new replacement parts fail or are bad out of box So don't rule that out. 

[DH15]

Finally got a chance to work on it today.  Turns out it was a bad fuel line between the fuel pump and fuel rail.  Replaced that and it runs great.